Important Transducer Characteristics
There are many characteristics that make up a successful and high quality Hall Effect transducer, or sensor. These needs to be brought together into one large package, to give you the best measurements and performance overall. Having said that, it’s worth talking about each one in turn, to truly understand the complex nature of this piece of measuring equipment.
When designers put together sensors for measuring magnetic field and powering movement, there is more to take into account than you may realise. There are also different types of sensor for different types of equipment to be measured.
Along with sensitivity and other particular issues which make a Hall Effect transducer successful or otherwise, there are three other particular characteristics to bear in mind – linearity, input and output resistances, and temperature coefficient of resistance. These sounds complicated in their titles, so let’s explore a little further to explain fully.
A Hall Effect sensor/transducer is a passive item, and that means that its main voltage on output is not able to be above the voltage that is inputted. Basically, if this occurs then you will have a sensitivity roll off, because there will be a slight discrepancy in the reading.
If you are taking a reading and the Hall Effect is small when compared to the bias voltage (when using direct current (DC) equipment), then the sensitivity can be very linear, e.g. straight. This will give you linear errors that are very low, e.g. less than 1%. This will give you a highly accurate reading. When measuring large magnetic fields, lower sensitivity Hall Effect transducers are best, because these don’t saturate, and give you a more accurate result in terms of linear effect.
Input and output resistances
This is mostly interesting to a person who is designing a Hall Effect transducer/sensor. This is because it will influence the design of the front of the amplifier on the sensor, which receives the signal. The input resistance is to do with the basic circuit board, whereas the output resistance is to do with the detection of the voltage.
If you attempt to design a transducer without going about the input and output resistances, then you are going to create a low quality, and lacking in accuracy piece of equipment.
Temperature coefficient of resistance
There is a direct relationship between the input and output resistances and the temperature coefficient, because they should match almost identically, if not extremely close to each other. When designing a Hall Effect transducer, if you know the temperature variation then you can easily design an accurate sensor.
A bias circuit (e.g. DC, direct current) piece of equipment is usually designed to be used with a transducer that has a particle resistance that sits mainly at room temperature. If this doesn’t happen and there are extremes in temperature, e.g. hot or cold, then variations in the reading can occur, and this is not what you want in terms of accuracy.
These are just three rather complicated characteristics that make up a successful and accurate Hall Effect transducer, or sensor. Designers work very closely with these characteristics, keeping in mind the piece of equipment that they are designed for. It’s certainly worthwhile mentioning that many sensors are not designed to be generic. This is because certain types of equipment require a more sensitive transducer, and others need something which is more about temperature coefficient. One size does not fit all, and a high quality sensor, or transducer needs to take into account several different areas of expertise, in order to give the best, and most accurate readings.